Alesis midiverb/quadraverb emulation...

[valhallasound]

I'm anticipating that this thread will be revived soon, so I might as well be the guy to do it. The reason:

http://noyzelab.blogspot.com/2014/11/sy ... part2.html

This is confirmation that Aphex Twin made heavy use of the Quadraverb. I've seen live footage of RDJ in the early 90s with a Quadraverb, but I've always thought that the SAWII reverb sound was from the Quadraverb.

Since this thread was last updated, I've done a LOT of work on the Spin Semiconductor FV-1 chip, which is in the Tiptop Audio Z-DSP module. The Halls of Valhalla reverb cartridge runs in the Z-DSP. As far as I know, the algorithms don't have much in common with the Alesis algorithms, except for Ginnungagap (which is probably similar to the Bloom algorithms from the Midiverb II). However, there is still a lot of sonic similarity between the Halls of Valhalla and the Alesis boxes. All of the algorithms have a certain Alesis "flavor."

My current theory is that the peculiarities of the FV-1 hardware are adding this coloration to any algorithms that run on them, and that these peculiarities are shared with the Alesis hardware. Keith Barr designed the ASICs used by both Alesis and Spin Semiconductor (with help from others), and there were a lot of tricks used in the design to reduce the cost of the silicon. Barr detailed a lot of these tricks in his book, "ASIC Design in the Silicon Sandbox":

http://www.amazon.com/ASIC-Design-Silic ... 623&sr=1-1

I've thought about how to simulate these quirks in 32-bit floating point realizations (i.e. plugins). I'm not sure if it is worth the effort, but I'll keep it on a back burner.

Sean Costello

[valhallasound]

Hello Sean,i remember from some of your talks with the late Keith Barr, you once mentioned that he replied in a email that Quadraverb used 4 parallel loops (2 x AP + 1 delay) ,outputs from delay taps...

Could midiverb/quadraverb used this algorithm?:



if so,would midiverb shared the same design?

thank you

Sérgio Frias

I don't know why I didn't read this diagram correctly. I though it was the unmodified diagram from the Spin Semi site, but you have changed it to show 4 parallel AP loops. This is probably correct. Sorry I didn't see this earlier. Add some series allpasses to the input, and a lowpass filter in each of the 4 loops, and you probably have something similar to the Quadraverb.

[sergiofrias]

thank you Sean
it's incredible how so simple algorithms can sound so great
Your work with Spin Semiconductor FV-1 sounds amazing ,i'm also intrigued with your hardware coloration theory ,could it be related to adc /dac or eeprom ?

[david.beholder]

Saw this video: https://www.youtube.com/watch?v=E2bS7Tw-l5Q

Wanted to figure out how to repro such verb with Valhalla Plugins. Found this thread.

[valhallasound]

Saw this video: https://www.youtube.com/watch?v=E2bS7Tw-l5Q

Wanted to figure out how to repro such verb with Valhalla Plugins. Found this thread.

Is that a cover of a BoC song? If so, which one? Tracking the original down is DRIVING ME CRAZY!!!

Anyway, the reverb in this song isn't as critical as the synth sound: The synth has a single LFO sweeping the filter, and _slightly_ modulating the pitch of the synth. This produces that characteristic BoC wobble. The reverb is probably Quadraverb. You could get there with Room or VintageVerb: tighter attack, medium decay, some modulation, turn down the high EQ.

[david.beholder]

Is that a cover of a BoC song? If so, which one? Tracking the original down is DRIVING ME CRAZY!!!

Listen carefully to notes of Telephasic Workshop from MHRTC

Anyway, the reverb in this song isn't as critical as the synth sound: The synth has a single LFO sweeping the filter, and _slightly_ modulating the pitch of the synth. This produces that characteristic BoC wobble. The reverb is probably Quadraverb. You could get there with Room or VintageVerb: tighter attack, medium decay, some modulation, turn down the high EQ.

I think you underestimate power of PWM on Alpha.

Quote from video about video:

Ryland, the patch is my own. I use a BCR2000 to program the Juno since the bubble-button interface is worth nothing. The sound is basically just a square with plenty of modulation on the pulse width.Tight decay on the filter env. ROland chorus is ON, obviously The LFO is also modulating the filter frequency (don't forget to add some resonance). The compression, overdrive and reverb is up to the Quadraverb.